which is also the syntax for the option as a BOOT.INI switch in earlier Windows
versions. Beware however that for the BOOT.INI switch,
address is not an address but a number of MB.

Behaviour

The Loader obtains from the firmware a map of physical memory. For BIOS machines,
the means of discovery is int 15h function E820h. The truncatememory
option simply tells the Loader to discard from this map every 4KB page that is not
entirely below the given address. The discarded
pages may as well not have been reported by the firmware.

This processing of the memory map is done very early by the Loader in order to
configure its own memory management. Although the truncatememory
option is reported in the Edit Boot Options Menu
and the corresponding switch, /MAXMEM, can be edited
or added, changes are too late to be acted on and are not respected.

The option is passed to the kernel as /MAXMEM but
both NTOSKRNL.EXE and NTKRNLPA.EXE ignore it.